1. Field of the Invention
This invention relates to a process for rolling structural shapes and to a rolling stand and a rolling mill for rolling the structural shapes according to the preferred process.
2. Description of the Prior Art
It is not uncommon for various structural shapes to be transformed from billets, ingots or slabs in several working stages and passes and finished to their final size. For decades, the processes described by Grey, Sack or Puppe ("Die Technik des Eisenhuttenwesens", 5th Edition, 1944, Verlag Stahleisen Dssseldorf, pp. 177, 178) have been used on universal rolling mills.
The Grey rolling mill, with two rolling stands arranged one behind the other, is still used today in rolling trains for H-piles, I-beams or double-tee structural shapes with dimensions up to 1000 mm, since additional stands would involve enormous tool costs. The horizontal rolls work the web and the flanges simultaneously, while two vertical rolls finish the outside of the flanges.
In the Puppe process, disclosed in German Pat. Nos. 254,977 and 307,856, the flanges are rolled in a somewhat outwardly-bent position and then bent back into their final position. This process is also used for rolling on finishing mills, for example, in the fabrication of smaller H-piles, I-beams, double-tee structural shapes or beams, or channels, tees or angles ("Hutte, Taschenbuch fur Eisenhuttenleute", 5th Edition, 1961, page 767, Verlag von Wilhelm Ernst & Sohn, Berlin). The process could also be used for shapes which, as a result of a notched configuration or undercutting of the structural shape, do not permit a direct fabrication process (German Pat. No. 240,433).
It does not appear that any significant improvements have heretofore been made to the Puppe principle. Quite modern rolling mills with modified technologies are disclosed in German Laid Open Pat. Nos. 29 36 680 and 35 21 949 and in U.S. Pat. Nos. 4,329,045 and 4,367,642. Such modern rolling mills use the principle of bending the flanges outwardly to prevent an offsetting of the web center on symmetrical shapes by bi-axial guidance of the structural shape.
The outward bending has the additional advantage of keeping the depth of indentation in the shaping roll low. As a result, the roll can be refinished more frequently and can be designed for a longer service life.
Both the Grey process and the Puppe process suffer from a serious disadvantage in the fabrication of beams with parallel flanges. The advantage of the Grey process, including its requirement for only a few rolls, is partly offset by the major friction wear to the shaping rolls because of the high relative speeds between the flange of the shapes and the shaping surfaces of the rolls. Additionally, the number of refinishings which can be performed on the roll is limited by the deeply indented shape, since the rolls must have a diameter within a specified range.
In the Puppe process for beams, and in fabrication processes for other structural shapes, this friction wear is significantly lower. However, at least one complete finishing stand must be installed for the final inward bending (final bending pass) of the outer shape segments.
Because of the reversing operation of the edging stand, the conventional finishing stand must be located at a distance of more than one length of rolling stock behind the final upsetting stand. As a result, such a rolling mill takes up a great deal of space.
All of the patents and publications mentioned above are incorporated herein by reference as if the entire contents thereof were fully set forth herein.